Mine roof support



July 967 Filed Aug. 21, 1964 MINE ROOF. S PORT 2 Sheets-Sh 1 INVE O R ALTER IKE BY July 4, 1967 W WEIRICH I 3,328,968

MINE ROOF SUPPORT Filed Aug. 21, 1964 2 sheets-sheet 2 U (3 N r l e 5 Q \s N Q X 9 I L 3 6 K) N n m INVENTOR Q R WA: 7512 #492101,

fluvial/e! Jai ATTORNEY United States Patent 3,328,968 MKNE ROOF SUPPORT Walter Weirich, Dortmund, Germany, assignor to Hoesch- Bergbautechnik G.m.b.H., Dortmund, Germany Filed Aug. 21, 1964, Ser. No. 391,149 Claims priority, application Germany, Aug. 23, 1963, H 50,084 Claims. (Cl. 61-45) The present invention relates to mining apparatus. More particularly, the invention relates to a mobile mine roof support which is utilized in underground coal mines or similar excavations and is provided with means for propping the roof of a mine shaft to prevent cave-in during removal of ore from the mine face.

Mobile or walking mine roof supports are well known in the art. Such apparatus comprise upright leading and trailing pit props which are extensible and contractible to move their caps, also called roof bars, into or away from engagement with the mine roof. The lower ends of the props are articulately connected to floor-engaging plates, also called sole plates or runners, which follow the outline of the mine floor and slide therealon-g when the apparatus is caused to walk toward the mine face. The device for advancing the apparatus normally comprises frame means of known construction as for instance shown in the British Patent 885,645 having one or more elongated horizontal hydraulic cylinders and pistons which are mounted lengthwise between the pairs of leading and trailing props and which are connected to the frame means to alternatingly advance the props on opposite sides of said frame means forward the mine face.

A serious problem arises in such apparatus when the mine floor is strongly inclined or when the mine floor is uneven, i.e., when it is full of holes and is covered with large pieces of ore, filling or rock, such as will cause the sole plates to be inclined with reference to a horizontal plane and to bring about a corresponding inclination of the props. The connections between the props and the sole plate or plates cannot be rigid because, otherwise, the entire mine roof support would be likely to overturn on an unven mine floor. On the other hand, the connections between the props and one or more sole plates cannot be too loose because the props would swing back and forth while the apparatus advances toward the mine face and the roof bars would be unlikely to automatically return to optimum positions for reengagement with the mine roof.

Accordingly, it is an important object of the present invention to provide improved connections between the props and the advancing device of a walking mine roof support, and to construct the connections in such a way that their parts may be readily exchanged, adjusted, inspected, repaired, or otherwise manipulated without necessitating complete dismantling of the mine roof support.

Another object of the invention is to provide connections of the just outlined characteristics which are constructed and assembled in such a way that they cause the props to automatically assume optimum positions for reengagement of their caps with the mine roof when the apparatus is at a standstill, irrespective of the inclination or roughness of the mine floor.

A further object of the invention is to provide a mine roof support wherein the props are coupled to each other and to the advancing device in such a way that their maximum inclination may be selected at the will of the operator so as to adapt the mine roof support to the conditions prevailing in a given underground excavation.

Still another object of the invention is to provide novel and readily adjustable coupling connections between the sole plates and the advancing device of a walking mine roof support and to construct the adjustable connections in such a way that the ability of sole plates to move with reference to the advancing device and/or with reference to the respective props may be regulated at the will of the operators.

A concomitant object of the present invention is to provide exceptionally simple, rugged, compact and comparatively inexpensive articulate connections between the props and the advancing device of a walking mine roof support and to construct the connections in such a way that they simultaneously couple the sole plates with the advancing device without in any way aifecting the desired mobility of the props.

Still another object of the invention is to provide a mine roof support wherein the improved articulate connections may be utilized with equal advantage irrespective of the exact number of props whereby the mine roof support may be provided with a single pair of leading props and a single pair of trailing props or with three or more pairs of such props.

A further object of the invention is to provide a mine roof support of the above outlined characteristics wherein the improved connections for the props and/or sole plates occupy space which is invariably available in an underground excavation, wherein the connections are highly resistant to wear and may be assembled of prefabricated parts, and wherein such connections may be manipulated by persons having comparatively little technical background.

With the above objects in view, one feature of the present invention resides in the provision of a walking mine roof support which comprises elongated horizontal advancing means arranged to move the support stepwise toward the mine face in an underground excavation, a pair of extensible and contractible leading pit props which are located at the opposite sides of the advancing means, a pair of extensible and contractible trailing pit props which also are located at the opposite sides of the advancing means, a floor-engaging, sole plate articulately connected to the lower end portion of each prop, and a novel articulate connection between the props, sole plates and advancing means. The connection comprises two laterally extending hinges which are connected to frame of the advancing means and include links or levers adapted to pivot about axes which are parallel with the longitudinal extension of the advancing means, and such links carry detachable resilient elements in the form of suitably configurated leaf springs which are assembled into two groups of packages, one at each side of the advancing means and each including an upper package and a lower package. The packages have forwardly and rearwardly extending arms and the arms of each upper package are articulately and detachably connected to median portions of the props at a level above the respective hinge. The arms of the lower packages are articulately and detachably connected with such sole plates which are located at the same side of the advancing means. In such manner, the sole plates and the packages are free to move with reference to each other and with reference to the advancing means, and the props are free to move not only with reference to the advancing means but also with reference to each other and with reference to the sole plates whereby their roof bars can yield to unexpected obstructions when the mine roof support is caused to advance toward the mine face, and the sole plates are also free to follow the outlines of an uneven mine floor. Furthermore, and while the props are free to perform limited movements with respect to positions in which their axes are normal or nearly normal to the plane of the mine roof, they are held against excessive swinging, tilting and similar movements such as could move the roof bars in positions in which they are unable FIG. 1 is a fragmentary side elevational view of a mobile mine roof support wherein the sole plates and the props are mounted in accordance with my invention;

FIG. 2 is a fragmentary top plan view of the mine roof support, with the roof bars omitted; and

FIG. 3 is a transverse vertical section as seen in the direction of arrows from the line III-III of FIG. 2.

Referring to the drawings, and first to FIG. 1, there is shown an apparatus known as a mobile or walking mine roof support which comprises a pair of leading hydraulic pit props 2 each of which is extensible and contractible in a manner well known in the art and each of which carries at its upper end a cap or roof bar (not shown) which is movable in actual engagement with the mine roof when the respective prop 2 is caused to extend. The lower ends of the props 2 are connected with sole plates 3, here shown as runners preferably having upwardly bent front end portions so that they may be caused to shufile along an uneven mine floor F. The connections between the props 2 and the sole plates 3 comprise ball and socket jointsof known design which enable the props to swivel in all directions in order to move their roof bars in requisite face-to-face abutment with the mine roof. The roof bars are articulately connected with the upper ends of the props 2 to further assist such roof bars to move in requisite positions with reference to the mine roof. FIG. 1 shows that the two leading props 2 are in transverse alignment with each other and are disposed at the opposite sides of an elongated horizontal advancing device 1 which serves to move the mine roof support along the mine floor F and in a direction to the left, i.e., toward the mine face (see the arrow A).

The mine roof support also comprises a pair of transversely aligned trailing hydraulic pit props 2 which are disposed at the opposite sides of a frame 10 of an advancing device. The later includes one or more cylinders mounted on the frame 1a which is connected with the props 2, 2 and an equal number of pistons. The manner in which the advancing device may operate to walk the mine roof support has been pointed out above.

The trailing props 2 are connected with sole plates 3 and with caps or roof bars (not shown) in the same way as described in connection with the leading props.

In accordance with my invention, the means for connecting the props 2, 2' and sole plates 3, 3' to the advancing device comprises a pair of hinges 4 (only 'one shown) which are fixed to the frame 1a of the advancing device, and four packages of detachable leaf springs 5, 6 which respectively connect one leading prop 2 with the corresponding trailing prop 2' and one leading sole plate 3 with the corresponding trailing sole plate 3. In other words, the props 2, 2' which are disposed at the same side of the frame 1a of the advancing device form a group of longitudinally aligned props which are connected to each other by an upper package 5, and the sole plates 3, 3' which are disposed at the same side of the advancing device are connected to each other by a lower package 6. The median portions of the packages are detachably connected to the respective hinge 4, and it will be noted that the packages 5, 6 are U-shaped or V-shaped whereby the end portions of their arms respectively extend upwardly and downwardly, i.e., above and below the level of the hinges 4.

Referring to FIGS. 2 and 3, it will be noted that each hinge 4 comprises a U-shaped bracket 4:: which is fixed to the frame 1a of the advancing device, a horizontal pivot pin 4b which is parallel to the longitudinal direction of the advancing device (i.e., the pins 41) extend in the direction indicated by the arrow A in which the mine roof support advances toward the mine face), a laterally extending link 40 whose inner end is pivotable on the pin 4b, and a wedge-like retaining element 4d which keeps the pin 4b in the axial position shown in FIGS. 2 and 3. The pin 4b extends through the legs of the U-shaped bracket 41:. The outer end of the link 4c is detachably connected with the median portions of the packages 5, 6 by means of a veertical pin 42 having at its upper end a diametral slot to receive a locking wedge 7. The head 4f at the lower end of the pin 4:: abuts against a suitable clamp 4g which engges the underside of the lower package 6. The horizontal pin 4b enables the packages 5, 6 of a group to pivot within limits about a horizontal axis which is parallel to and is spaced laterally from the frame 1a.

The front arm 6a of the lower package 6 shown in FIGS. 1 to 3 is articulately and detachably connected to the leading sole plate 3 of the corresponding leading prop 2 by means of a coupling device including a horizontal pintle 13 which is normal to the pivot pin 4b. The pintle 13 extends through an eye provided on the front arm 6a and through one of the openings 13a provided in a rearwardly extending plate-like lug 3a of the leading sole plate 3. It will be noted that the lug 3a is provided with a plurality of spaced openings 13a so that the position of the pintle 13 may be changed, depending on the length of the arm 6a and on the desired stressing of the lower package 6. The trailing arm 6b of the package 6 shown in FIGS. 1 to 3 is articulately and detachably connected with a forwardly extending lug 3b provided on the trailing sole plate 3'. This lug has several horizontal openings 14 one of which receives a transversely extending coupling element here shown as a pintle and serving to connect the lug 3b with the trailing arm 6b. Thus, the sole plates 3, 3' are free to pivot with reference to the package 6 about horizontal axes which are perpendicular to the axis of the pivot pin 4b, but the bias of the package 6 is strong enough to limit such pivotal movements of the sole plates or to immediately return the sole plates to positions in which the props 2, 2 may be vertical or nearly vertical. In other words, the leaves of the package 6 contribute to retention of the props in requisite positions for satisfactory engagement of their roof bars with the mine roof. Also, the leaves of the package 6 prevent excessive swinging of the props when the advancing device is caused to move the mine roof support in a direction to the left, as viewed in FIG. 1, and toward the mine face. The end portions of the arms 6a, 6b are located at a level below the corresponding hinge 4.

The upper package 5 comprises a forwardly and upwardly extending arm 5a which is articulately and detachably connected with a median portion of the corresponding leading prop 2. The coupling between the arm 5a and the prop 2 comprises a U-shaped shackle 11 which straddles a median portion of the prop 2 at a level well above the corresponding sole plate 3 and above the level of the hinges 4. The end portion of the arm 5a carries an attachment 10 which is detachably secured to the shackle 11 by fasteners 12 of any known design. To prop 2 is preferably free to perform limited angular and axial movements with reference to the leading arm 5a to make sure that it may move its roof bar to an optimum position of inclination with reference to the mine roof. The arm 5b of the upper package 5 shown in FIGS. 1 to 3 comprises an attachment 8 for rearwardly extending fasteners 12a which connect it to a shackle 11a straddling the median portion of the corresponding trailing prop 2' at a level above the hinges 4.

It is clear that the number of leaves in the packages 5 and/ or 6 may be selected at the will of the manufacturer so that such packages will offer a predetermined resistance to deformation of the mine roof support. Also, the leaves may be made of different materials to change the elasticity of the packages. Furthermore, the operators may change the elasticity of the packages by inserting and clamping wedge-like spacers between the median portions which are traversed by the vertical pin 4e. Moreover, the deformability of the entire mine roof support may be changed by utilizing packages 5, 6 whose shape (in undeformed condition) is different from the shapes shown in FIG. 1. Thus, if the upwardly extending end portions of the arms 50, 5b are shorter, the shackles 11, 11a will be located at a lower level and the props 2, 2 will have less freedom to wobble with reference to a vertical position. The overallv length of the packages 5, 6 will determine the distance between the pairs of leading and trailing props 2, 2, i.e., the entire mine roof support may be made shorter or longer by replacing the packages 5 and 6 with differently dimensioned and/or configurated packages.

The distance between the sole plates 3, 3' of FIGS. 1 to 3 may be adjusted by inserting the pintles 9, 13 into a different set of openings 14, 13a. In such instances, the upper package 5 should normally be replaced by a different package, or the fasteners 12 must be replaced by shorter fasteners. Of course, and since the roof bars are preferably coupled to each other, the operators will replace the roof bars by a different set whenever they decide that the distance between the sole plates 3 and 3' must be. changed.

It will be noted that the bias of the upper package 5 upon the props 2 and 2' is independent of the bias of lower arms 6a, 6b upon the sole plates 3, 3'. Therefore, and when the mine floor is substantially horizontal, the arms 50!, 5b of the upper package may automatically return the props to vertical or nearly vertical positions as soon as the roof bars are disengaged from the mine roof, i.e., the props will immediately return to positions in which their roof bars are in requisite positions with reference to each other and with reference to the mine roof. The same applies for the lower package 6 which controls the positions of the sole plates and which operates independently of the upper package. The arms 5a, 5b of the upper package will yield when the roof bars meet an obstruction while the mine roof support is caused to advance toward the mine face. In other words, if the roof bars meet an obstruction at the time the .props 2 and/or 2 are contracted, they need not be detached from the props because the arms 5a, 5b will yield and will allow the roof bars to bypass the obstruction.

It goes without saying that each hinge 4 may be replaced by a pair of hinges or by three or even more hinges. Thus, the median portions of the packages 5, 6 shown in FIG. 1 may be connected to a pair of hinges which are spaced from each other in the longitudinal direction of the frame 1a. However, even if a hinge 4 is replaced by two hinges, the distance between such hinges is preferably less than the length of the legs 5a, 5b, 6a and 6b. This insures that the sole plates and the props will have sufficient freedom of movement from their normal positions and enables the mine roof support to operate properly on a mine floor which is full of holes or which is covered with fragments of rock or filling, as well as in underground excavations whose roof exhibits pronounced unevennesses such as will cause the roof bars to take different positions of inclination with reference to a normal position in which the plane of a roof bar is perpendicular to the axis of the corresponding prop.

If the mine roof support comprises one or more additional pairs of transversely aligned pit props which are located behind the trailing props 2, the additional p rops may be coupled to the frame 10 in the same way as described in connection with FIGS. 1 to 3.

It will be noted that the end portions of the arms 5a, 5b are bent upwardly and that the end portions of the arms 6a, 6b extend downwardly. This is of advantage because the packages 5, 6 can withstand higher torsional stresses.

The couplings between the sole plates 3, 3 and the arms 6a, 6b of the lower packages 6 enable the operators to move the props 2, 2' to inclined positions if the configuration of the mine roof and/ or mine floor F is such that an incline-d prop is more likely to offer satisfactory resistance to cave-in. In other words, merely by inserting the pintles 9, 13 into a different set of openings 14, 13a, the operators may change the normal inclination of the corresponding props without necessitating replacement of the upper packages 5. Also, and in order to allow for further adjustments in the inclination of the props 2 and 2', the couplings including the shackles 11, 11a, attachments 8, 10 and fasteners 12, 12a preferably adjustable so that the inclination of the props may be changed even if the connections between the lower packages 6 and the corresponding sole plates 3, 3' remain unchanged.

The packages 5, 6 are strong enough to maintain the props in \requisite position even if the mine floor is strongly inclined with reference to a horizontal plane. In such inclined underground excavations, the props tend to overturn as soon as they are disengaged from the mine roof and they often assume positions in which the roof bars are out of proper engagement with the mine roof. The packages 5 and 6 may be readily dimensioned, mounted and configurated in such a way that theprops tend to remain in positions in which their axes are substantially perpendicular to the mine roof, even when the excavation is inclined very strongly with reference to a horizontal plane. On the other hand, the improved connections between the lower packages and the sole plates insure that the sole plates may readily follow the outlines of an uneven mine floor while the props remain in optimum positions for engagement of their roof bars with the mine roof. The upwardly and downwardly'inclined end portions of the arms 5a, 5b, 6a, 6b prevent excessive tilting of props in inclined excavations but the remainder of each arm still enables the respective package to flex sufliciently and to allow for some tilting of the props which will be necessary to bypass certain obstruction without damage to the apparatus. Since the inclination of the floor with reference to a horizontal plane is normally small, the end portions 5a, 5b of the upper packages 5 will automatically keep the props from swinging when the apparatus is caused to advance along an uneven mine floor which might be substantially horizontal but is full of holes and is covered with pieces of rock which would normally cause the props to swing while the apparatus moves toward the mine face.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of this invention, and therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a mobile mine roof support, in combination, elongated frame means; two groups of props each adjacent to one side of said frame means and each including a leading prop and a trailing prop, each of said props having a lower end portion; a floor-engaging sole plate articulately connected to the lower end portion of each prop; two groups of elongated springs disposed at the opposite sides of said frame means and each including a first spring having end portions articulately connected to the respective sole plates and a second spring having end portions located spaced from and above the level of said sole plates and articulately connected to the respective props; and a pair of hinges each articulately connecting one of said groups of springs to said frame means intermediate said leading and trailing props and at a level above the level of said sole plates.

2. In a mobile mine roof support, in combination, elongated frame means; two groups of props each adjacent to one side of said frame means and each including a leading prop and a trailing prop, each of said props having a lower end portion; a floor-engaging sole plate articulately connected to the lower end portion of each prop; two groups of elongated springs disposed at opposite sides of said frame means and each including a first spring having end portions articulately connected to the respective sole plates and a second spring having end portions located spaced from and above the level of said sole plates and articulately connected to the respective props; a pair of hinges each articulately connecting one of said groups of springs of said frame means intermediate said leading and trailing props and at a level above the level of said sole plates; and means for detachably connecting said groups of springs to the respective hinges.

3. In a mobile mine roof support, in combination, elongated substantially horizontal frame means; two groups of upright pit props each adjacent to one side of said frame means and each including a leading prop and a trailing prop, each of said props extending above said frame means and each having a lower end portion; a floor-engaging sole plate articulately connected to the lower end portion of each prop; two groups of elongated springs disposed at the opposite sides of said frame means and each including a lower spring having end portions articulately connected to the respective sole plates and an upper spring having end portions articulately connected to the respective props at a level above said frame means; and a pair of hinges for articulately connecting said groups of springs to said frame means intermediate said leading and trailing props and at a level above the level of said sole plates.

4. In a mobile mine roof support, in combination, elongated substantially horizontal frame means; two groups of upright pit props each adjacent to one side of said frame means and each including a leading prop and at trailing prop, each of said props extending above said frame means and each having a lower end portion; a sole plate articulately connected to the lower end portion of each prop; two groups of elongated leaf springs disposed at the opposite sides of said frame means and each including an upper spring and a lower spring, each of said springs having two end portions and a median portion; first coupling means for articulately connecting the end portions of said upper springs to said props at a level above the level of said sole plates; second coupling means for articulately connecting the end portions of said lower springs to said sole plates; first hinge means for articulately connecting the median portions of one group of springs to said frame means; and second hinge means for articulately connecting the median portions of the other group of springs to said frame means so that the springs of each group are pivotable about axes which are substantially parallel with the longitudinal extension of said frame means.

5. In a mobile mine roof support in combination; elongated substantially horizontal frame means; two groups of upright pit props each adjacent to one side of said frame means and each including a leading prop and a trailing prop, each of said props extending above said frame means and each having a lower end portion; a sole plate articulately connected to the lower end portion of each prop; two groups of elongated leaf springs disposed at the opposite sides of said frame means and each including an upper spring and a lower spring, each of said springs having two end portions and a median portion; first adjustable coupling means for articulately connecting the end portions of said upper springs to said props at a level above the level of said sole plates and in such a way that the distance between said leading and trailing props may be changed, second adjustable coupling means for articulately connecting the end portions of said lower springs to said sole plates in such a way that the distance between the sole plates of said leading and trailing props may be changed; first hinge means for articulately connecting the median portions of one group of springs to said frame means; and second hinge means for articulately connecting the median portions of the other group of springs to said frame means so that the springs of each group are pivotable about axes which are substantially parallel with the longitudinal extension of said frame means.

6. In a walking mine roof support, in combination, elongated substantially horizontal frame means; two groups of upright pit props each adjacent to one side of said frame means and each including a leading prop and a trailing prop, each of said props extending above said frame means and each having a lower end portion; a sole plate articulately connected to the lower end portion of each prop; two groups of elongated resilient elements disposed at the opposite sides of said frame means and each including an upper package of leaf springs and a lower package of leaf springs, each of said packages having a median portion and a pair of end portions; first coupling means for articulately connecting the end portions of said lower packages to the respective sole plates; second coupling means for articulately connecting the end portions of said upper packages to the respective props at a level above said frame means; first hinge means for articulately connecting the median portions of one group of said packages to said frame means; and second hinge means for articulately connecting the median portions of the other group of packages to said frame means so that said props are movable with reference to said frame means, with reference to each other, and with reference to the corresponding sole plates.

7. In a walking mine roof support, in combination, elongated substantially horizontal frame means; two groups of upright pit props each adjacent to one side of said frame means and each including a leading prop and a trailing prop, each of said props extending above said frame means and each having a lower end portion; a sole plate articulately connected to the lower end portion of each prop; two groups of elongated resilient elements disposed at the opposite sides of said frame means and each including an upper package of leaf springs and a lower package of leaf springs, each of said packages having a median portion and a pair of end portions; first coupling means for articulately connecting the end portions of said lower packages to the respective sole plates; second coupling means for articulately connecting the end portions of said upper packages to the respective props at a level above said frame means, said second coupling means comprising shackles straddling and slidable along the respective props; first hinge means for articulately connecting the median portions of one group of said packages to said advancing means; and second hinge means for articulately eonnecting the median portions of the other group of packages to said advancing means so that said props are movable with reference to said advancing means, with reference to each other, and with reference to the corresponding sole plates.

8. In a walking mine roof support, in combination, elongated substantially horizontal frame means; two groups of upright pit props each adjacent to one side of said frame means and each including a leading prop and a trailing prop, each of said props extending above said frame means and each having a lower end portion; a sole plate articulately connected to the lower end portion of each prop; two groups of elongated resilient elements at the opposite sides of said frame means and each including an upper package of leaf springs and a lower package of leaf springs, each of said packages having a median portion and a pair of end portions; first coupling means for articulately connecting the end portions of said lower packages to the respective sole plates so that each sole plate is pivotable about a substantially horizontal axis which is perpendicular to the longitudinal extension of said frame means; second coupling means for articulately connecting the end portions of said upper packages to the respective props at a level above said frame means; first hinge means for articulately connecting the median portions of one group of said packages to said frame means so that the packages of said one group are pivotable about an axis which is parallel with the longitudinal extension of said frame means; and second hinge means for articulately connecting the median portions of the other group of packages to said frame means so that the packages of said other group are pivotable about an axis which is parallel with the longitudinal extension of said frame means.

9. A structure as set forth in claim 8, wherein the end portions of said upper packages are bent upwardly and the end portions of said lower packages are bent downwardly.

10. In a walking mine roof support, in combination, elongated substantially horizontal frame means; two groups of upright pit props each adjacent to one side of said frame means and each including a leading prop and a trailing prop, each of said props extending above said frame means and each having a lower portion; a sole plate articulately connected to the lower end portion of each prop; two groups of elongated resilient elements disposed at the opposite sides of said frame means and each including an upper pack-age of leaf springs and a lower package of leaf springs, each of said packages having a median portion and a pair of end portions; first coupling means for articulately connecting the end portions of said lower packages to the respective sole plates; second coupling means for articulately connecting the end portions of said upper packages to the respective props at a level above the level of said sole plates and at a variable distance from the respective sole plate; first hinge means for articulately connecting the median portions of one group of said packages to said frame means; and second hinge means for articulately connecting the median portions of the other group of packages to said frame means so that said props are movable with reference to said frame means, with reference to each other, and with reference to the corresponding sole plates.

References Cited UNITED STATES PATENTS 3,192,722 7/1965 Hermann et al. 6145.2 3,218,811 11/1965 Barall et a1. 61-45.2

FOREIGN PATENTS 858,633 1/1961 Great Britain.

DAVID J. WILLIAMOWSKY, Primary Examiner. JACOB SHAPIRO, Examiner. 

1. IN A MOBILE MINE ROOF SUPPORT, IN COMBINATION, ELONGATED FRAME MEANS; TWO GROUPS OF PROPS EACH ADJACENT TO ONE SIDE OF SAID FRAME MEANS AND EACH INCLUDING A LEADING PROP AND A TRAILING PROP, EACH OF SAID PROPS HAVING A LOWER END PORTION; A FLOOR-ENGAGING SOLE PLATE ARTICULATELY CONNECTED TO THE LOWER END PORTION OF EACH PROP; TWO GROUPS OF ELONGATED SPRINGS DISPOSED AT THE OPPOSITE SIDES OF SAID FRAME MEANS AND EACH INCLUDING A FIRST SPRING HAVING END PORTIONS ARTICULATELY CONNECTED TO THE RESPECTIVE SOLE PLATES AND A SECOND SPRING HAVING END PORTIONS LOCATED SPACED FROM AND ABOVE THE LEVEL OF SAID SOLE PLATES AND ARTICULATELY CONNECTED TO THE RESPECTIVE PROPS; AND A PAIR OF HINGES EACH ARTICULATELY CONNECTING ONE OF SAID GROUPS OF SPRINGS TO SAID FRAME MEANS INTERMEDIATE SAID LEADING AND TRAILING PROPS AND AT A LEVEL ABOVE THE LEVEL OF SAID SOLE PLATES. 